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Discussion Starter · #1 ·
Hey guys, I have a 1.8t in a MK4. I am getting the code "P0411: Secondary Air Injection Upstream Flow Detected". It usually comes on after I get off the freeway on my drive to school, so about 10 minutes after starting, well after the SAI System stops running. I have noticed no other noises or excessive loudness from the engine. Anyone have ideas?

Zach!

 

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Discussion Starter · #4 ·
how long the cone filter ben on there what other mods? e.cu. have anything done to it?have u tried to let it warm up before u drive on freeway?:what:
The filter has been on there for about a year and a half, in its current form and on a CAI tube. Other mods are just a 3" downpipe, a boost gauge, VAC res relocate. It is always warmed up before I get to the freeway. I try to stay sitting until the SAI turns off in the morning
 

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Are you sure that's the correct fault code? P0411 is "Secondary Air Injection System: Incorrect Flow Detected" which usually means the vacuum line to the combi-valve is leaking
Yup.

Another thing also is it may be the vacuum tube that connects to the side of the airbox (passenger side) may be loose/broken/disconnected.
 

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Discussion Starter · #7 ·
Yup.

Another thing also is it may be the vacuum tube that connects to the side of the airbox (passenger side) may be loose/broken/disconnected.
Thanks guys, I have a breather filter on the SAI that has been fine for over a year, i'm thinking it could be the combi valve or line near it, i'll take a look!
 

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The most common issue is that the combi valve either freezes open or closed. you can test this by applying vacuum directly to the combi valave and trying to blow through it at the same time. When there is no vacuum on the valve you shouldn't be able to blow through it. I have also seen the air pump fill with water when the valve sticks open and nothing is done about it for years. So its always a good idea to pull off the lower hose for the air pump and see if liquid comes out. Also have you verified that the air pump is infact running?
 

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The most common issue is that the combi valve either freezes open or closed. you can test this by applying vacuum directly to the combi valave and trying to blow through it at the same time. When there is no vacuum on the valve you shouldn't be able to blow through it. I have also seen the air pump fill with water when the valve sticks open and nothing is done about it for years. So its always a good idea to pull off the lower hose for the air pump and see if liquid comes out. Also have you verified that the air pump is infact running?

Beat me to it....exactly what I was going to say.
 

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Are you sure that's the correct fault code? P0411 is "Secondary Air Injection System: Incorrect Flow Detected" which usually means the vacuum line to the combi-valve is leaking
The most common issue is that the combi valve either freezes open or closed. you can test this by applying vacuum directly to the combi valave and trying to blow through it at the same time. When there is no vacuum on the valve you shouldn't be able to blow through it. I have also seen the air pump fill with water when the valve sticks open and nothing is done about it for years. So its always a good idea to pull off the lower hose for the air pump and see if liquid comes out. Also have you verified that the air pump is infact running?
I am also pulling this code and these are finally the best (and consolidated haha) answers I've found! Thanks I'll check this out soon and post up my results.
 

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just pull as much vacuum as it can usually 20 inches or so and then test it. Remember with no vacuum you shouldn't be able to blow through it with a vacuum on it you should. if there is no difference between vac and no vac its frozen.
 
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